December 1981

Purchase To Read More

Digital Issue ?Read or download this issue’s articles online. *A printed copy of this issue is not included. $7.99

Print + Digital All Access Subscription ?Read or download this issue’s articles online. Plus, subscribe to get Print, Online and Tablet access to the next 12 new issues to be released as well as Online access to archives back to 1845. $99.00

Features

Laser Weapons

Could orbiting lasers defend a nation against missile attack?
The technological obstacles are insurmountable; furthermore, such weapons would be vulnerable to simple countermeasures

By Kosta Tsipis

Magnetic Navigation in Bacteria

Certain aquatic bacteria are magnetotactic: they have tiny internal compasses that orient them in the earth's magnetic field. Swimming along the inclined magnetic field lines directs them toward the mud

By Richard B. Frankel and Richard P. Blakemore

The Recumbent Stone Circles of Scotland

These megalithic monuments, like many others, have been seen as ancient astronomical observatories. It seems clear that although they are astronomically aligned, their purpose was purely ritual

By Aubrey Burl

Jupiter and Saturn

Competing models seek to describe the sun's two giant companions. In one model the winds are confined to a thin layer at the surface; in another the winds extend through the fluid depths of each planet

By Andrew P. Ingersoll

The Hearing of the Barn Owl

The bird exploits diikrences between the sound in its left and right ears to find mice in the dark. It can localize sounds more accurately than any other species that has been tested

By Eric I. Knudsen

Fibrinogen and Fibrin

The plasma protein fibrinogen is converted into fibrin to form a blood clot. In time the clot breaks down. Both processes can now be understood in terms of the detailed structure of the protein

By Russell F. Doolittle

Computer Algebra

Symbols as well as numbers can be manipulated by a computer.
New, general-purpose algorithms can undertake a wide variety of routine mathematical work and solve intractable problems

By Richard Pavelle, Michael Rothstein and John Fitch

The Anthropic Principle

Certain conditions, such as temperature, were favorable to the emergence of life on the earth. The anthropic principle argues the reverse: the presence of life may "explain" the conditions

By George Gale

Departments

50 and 100 Years Ago: December 1981

Science and the Citizen, December 1981

Letters

Letters to the Editors, December 1981

Recommended

Books, December 1981

Mathematical Recreation

Mathematical Games, December 1981

Amateur Scientist

The Amateur Scientist, December 1981

Departments

The Authors, December 1981

Annual Index 1981

Bibliography, December 1981

Purchase To Read More

Digital Issue ?Read or download this issue’s articles online. *A printed copy of this issue is not included. $7.99

Print + Digital All Access Subscription ?Read or download this issue’s articles online. Plus, subscribe to get Print, Online and Tablet access to the next 12 new issues to be released as well as Online access to archives back to 1845. $99.00

Expertise. Insights. Illumination.

Discover world-changing science. Explore our digital archive back to 1845, including articles by more than 150 Nobel Prize winners.

Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at www.springernature.com/us). Scientific American maintains a strict policy of editorial independence in reporting developments in science to our readers.